Обсуждение: When are SQL functions inlined & how can I tell?

I've been having some serious (> 100x) slowness in some of my code
which uses nice maintainable little SQL functions versus when I do
the same code as a big messy expression.  I got rid of STRICT, I've
tried STABLE and even IMMUTABLE and I can't seem to get the speed
difference to go away, so here are some questions:

(1) What are the current criteria for when an SQL function called
within another SQL function will be inlined?

(2) Is there some easy way to tell without massive logging whether
a particular function has been inlined?  I've tried doing various

EXPLAIN ... SELECT foo(...);

kinds of things where foo() calls bar() and I don't see that I can
tell anything about the inline status of either function.

Thanks,

_Greg

J. Greg Davidson

"J. Greg Davidson" <jgd@well.com> writes:
> (1) What are the current criteria for when an SQL function called
> within another SQL function will be inlined?

It depends on a number of things, not least which PG version you're
talking about.  When in doubt, consult the source code (see
inline_function or inline_set_returning_function in
src/backend/optimizer/util/clauses.c)

> (2) Is there some easy way to tell without massive logging whether
> a particular function has been inlined?  I've tried doing various

> EXPLAIN ... SELECT foo(...);

> kinds of things where foo() calls bar() and I don't see that I can
> tell anything about the inline status of either function.

Try EXPLAIN VERBOSE.  You should see either the function or its
expansion.

            regards, tom lane